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Biomedical subjects

D A Eberhard

Publications and source records attributed to D A Eberhard.

16 recordsLinked to original sources
PubMed2001

Overexpression of the retinoic acid-responsive gene Stra6 in human cancers and its synergistic induction by Wnt-1 and retinoic acid.

Genetic defects in the Wnt-1 signaling pathway contribute to human tumor progression and are especially prevalent in colorectal cancer. We screened mouse C57MG cells to isolate mRNAs induced by Wnt-1 and identified Stra6, an mRNA known to be up-regulated by retinoic acid. Up-regulation of Stra6 mRNA was also observed in hyperplastic mammary tissue and mammary gland tumors from transgenic mice expressing Wnt-1 and in human tumors that frequently harbor defects in Wnt-1 signaling. Stimulation of C57MG cells with retinoic acid plus Wnt-1 resulted in expression of Stra6 transcript to levels greatly exceeding that observed with either stimulus alone. This synergy could be explained in part by the up-regulation of retinoic acid receptor-gamma that was observed in response to Wnt-1 signaling. Accordingly, treatment of human colorectal cancer cell lines with retinoic acid resulted in the up-regulation of Stra6 mRNA and accumulation of Stra6 protein at the cell membrane. The data support a model in which Wnt-1 signaling synergizes with retinoids to activate retinoic acid receptor-gamma-responsive genes in human cancers.

Adenocarcinoma↗
PubMed2001

Control of the nuclear-cytoplasmic partitioning of annexin II by a nuclear export signal and by p11 binding.

This study investigated mechanisms controlling the nuclear-cytoplasmic partitioning of annexin II (AnxII). AnxII and its ligand, p11, were localized by immunofluorescence to the cytoplasmic compartment of U1242MG cells, with minimal AnxII or p11 detected within nuclei. Similarly, GFP-AnxII and GFP-p11 chimeras localized to the endogenous proteins. Likewise, GFP-AnxII(1-22) was excluded from nuclei, whereas GFP-AnxII(23-338) and GFP alone were distributed throughout the cells. Immunoprecipitation and biochemical studies showed that GFP-AnxII did not form heteromeric complexes with endogenous p11 and AnxII. Thus, the AnxII N-tail is necessary and sufficient to cause nuclear exclusion of the GFP fusion protein but this does not involve p11 binding. A nuclear export signal consensus sequence was found in the AnxII 3-12 region. The consensus mutant GFP-AnxII(L10A/L12A) confirmed that these residues are necessary for nuclear exclusion. The nuclear exclusion of GFP-AnxII(1-22) was temperature-dependent and reversible, and the nuclear export inhibitor leptomycin B (LmB) caused GFP-AnxII or overexpressed AnxII monomer to accumulate in nuclei. Therefore, AnxII monomer can enter the nucleus and is actively exported. However, LmB had little effect on the localization of AnxII/p11 complex in U1242MG cells, indicating that the complex is sequestered in the cytoplasm. By contrast, LmB treatment of v-src-transformed fibroblasts caused endogenous AnxII to accumulate in nuclei. The LmB-induced nuclear accumulation of AnxII was accelerated by pervanadate and inhibited by genistein, suggesting that phosphorylation promotes nuclear entry of AnxII. Thus, nuclear exclusion of AnxII results from nuclear export of the monomer and sequestration of AnxII/p11 complex, and may be modulated by phosphorylation.

Active Transport, Cell Nucleus↗
PubMed2000

Complete inhibition of rhabdomyosarcoma xenograft growth and neovascularization requires blockade of both tumor and host vascular endothelial growth factor.

Growth of the human rhabdomyosarcoma A673 cell line in nude mice is substantially reduced but not completely suppressed after systemic administration of the antihuman vascular endothelial growth factor (VEGF) monoclonal antibody (Mab) A.4.6.1. Potentially, such escape might be attributable to incomplete local penetration of the antibody because of a diffusion barrier associated with tumor growth. Alternatively, it might reflect a compensatory up-regulation of murine VEGF, produced by the stroma of the host, or of other angiogenic factor genes. To test these potential mechanisms, systemic administration of Mab A.4.6.1, was performed in conjunction with intratumoral administration of an irrelevant antibody, an antihuman VEGF Fab or mFlt(1-3)-IgG that neutralizes both human and murine VEGF. Tumor growth in the systemic-plus-intratumoral anti-VEGF group was not different from that in the systemic anti-VEGF-plus-intratumoral-control antibody group, arguing against the possibility that bioavailability is the factor that limits the antitumor efficacy of Mab A.4.6.1. However, intratumoral mFlt(l-3)-IgG administration dramatically enhanced the activity of systemic anti-VEGF Mab and resulted in complete suppression of tumor growth, which indicated that host VEGF significantly contributes to tumor growth. Systemic administration of mFlt(1-3)-IgG alone replicated these findings. Histological analysis of residual tumor tissues revealed an almost complete absence of host-derived vasculature and massive tumor-cell necrosis in the mFlt(1-3)-IgG groups. Such extensive necrotic areas were not present in the other groups. Real-time reverse transcription-PCR analysis of total RNA derived from tumor tissues indicated strong up-regulation of both human and murine VEGF as well as other genes regulated by hypoxia. Our findings emphasize the need to completely block VEGF for maximal inhibition of tumor growth.

Animals↗
PubMed1998

Annexins I and II bind to lipid A: a possible role in the inhibition of endotoxins.

Annexins are Ca2+-dependent phospholipid-binding proteins with anti-inflammatory properties that are present on the surfaces of, and released from, certain cell types, such as leukocytes and secretory epithelia. The present study investigated the possibility that annexins may bind directly to bacterial endotoxin, inhibiting its interactions with cellular receptors or accessory binding proteins. An enzyme-linked immunoassay demonstrated calcium-dependent binding of low nanomolar concentrations of annexin-I and annexin-II p36/p11 heterotetramer to lipid A. In contrast, little or no annexin binding to lipopolysaccharide (LPS) was detected under similar conditions. LPS-binding protein binding to lipid A was blocked by annexin-I, and the annexins inhibited nitrite generation in RAW 264.7 cells induced by lipid A but not that induced by LPS. The data suggest that direct binding of annexins to lipid A may represent a mechanism for suppressing cellular and systemic responses to endotoxin.

Animals↗
PubMed1997

Histopathology of arteriovenous malformations after gamma knife radiosurgery.

Stereotactic radiosurgery effectively obliterates many arteriovenous malformations (AVMs). Hemodynamic changes in AVMs after radiosurgery have been illustrated using magnetic resonance imaging and angiography, but there have been no detailed reports describing the underlying histopathological changes. This study examines AVMs at various times after gamma knife radiosurgery (GKRS) and describes the histopathological changes that lead to vessel occlusion. The authors examined nine AVM specimens obtained 10 months to more than 5 years after GKRS, by using routine histopathological stains as well as immunohistochemical techniques to detect smooth-muscle actin, factor VIII, and type IV collagen. Blood vessels within the AVMs showed progressive changes leading to narrowing or obliteration of the lumen. The earliest changes after gamma knife irradiation appear to be damage to endothelial cells, followed by progressive thickening of the intimal layer caused by proliferation of smooth-muscle cells that elaborate an extracellular matrix that includes type IV collagen. Finally, cellular degeneration and hyaline transformation occur. For statistical correlation analyses, the specimens were graded according to the degree of histopathological change and the relative number of vessels showing such changes. Both of these parameters were significantly correlated with time after GKRS and with AVM size reduction shown on follow-up imaging studies. Gamma knife radiosurgery of AVMs causes endothelial damage, which induces the proliferation of smooth-muscle cells and the elaboration of extracellular collagen by these cells, which leads to progressive stenosis and obliteration of the AVM nidus. This series of pathological changes in AVMs after GKRS is essentially similar to the response-to-injury model of atherosclerosis.

Actins↗
PubMed1996

Primary angiitis of the central nervous system associated with cerebral amyloid angiopathy: report of two cases and review of the literature.

Early diagnosis is essential for the effective management of primary angiitis of the CNS (PACNS), but the presence of cerebrovascular amyloid angiopathy (CAA) may complicate the pathologic diagnosis since nonvasculitic inflammatory reactions can accompany CAA. We report two patients with PACNS associated with CAA in whom the progression of symptoms ceased during combined corticosteroid/cyclophosphamide therapy. One patient had prominent eosinophilic vasculitis and eosinophilic CSF pleocytosis. Based on review of reported cases, features supporting the diagnosis of symptomatic vasculitis in these patients include subacute progression of mental status changes and multifocal deficits, elevated ESR and CSF protein, and multifocal nonhemorrhagic lesions on imaging studies. We conclude that combined disease (PACNS/CAA) is similar to PACNS and probably occurs more frequently than expected by coincidence. The presence of CAA should not alter the treatment strategy in patients presenting with symptoms and laboratory studies consistent with PACNS.

Aged↗
PubMed1994

Alterations of annexin expression in pathological neuronal and glial reactions. Immunohistochemical localization of annexins I, II (p36 and p11 subunits), IV, and VI in the human hippocampus.

Annexins are Ca(2+)-dependent membrane-binding proteins that are potentially important in Ca(2+)-induced neurotoxicity or neuroprotection. To address the possible involvement of annexins in cellular reactions to brain injury and neurodegenerative disease, we studied the immunohistochemical localization of annexins I, II (p36 and p11), IV, and VI in the adult human hippocampus. Formalin-fixed, paraffin-embedded tissue from autopsy cases representing hypoxic-ischemic injury, seizure disorders, Alzheimer's disease, and age-related controls were examined. Neurons showed cytoplasmic immunoreactivity for annexin I, whereas annexin VI was distributed in patterns suggesting plasma membrane and perisynaptic locations. The cytoarchitectural distribution of annexin VI within neurons was altered in pathological states and annexin VI was strongly associated with neuronal granulovacuolar bodies in Alzheimer's disease. Reactive astrocytes expressed annexins I, II (p36 and p11), and IV, whereas quiescent astrocytes were minimally immunoreactive. Significant annexin immunoreactivity was also detected in oligodendrocytes (annexin IV), ependymocytes (I, II, and IV), choroid plexus (I, IV, and VI), meningothelium (I, II, IV, and VI), and vascular endothelium (II and IV) and smooth muscle (I, IV, and VI). This is the first comparative study of immunoreactivities for multiple annexins in human brain. Neurons and glia display selective and different profiles of annexin protein expression and show immunohistochemical changes in pathological conditions, which suggest involvement of annexins in neuronal and glial reactions to injury.

Adult↗
PubMed1991

Regulation of the formation of inositol phosphates by calcium, guanine nucleotides and ATP in digitonin-permeabilized bovine adrenal chromaffin cells.

Both micromolar Ca2+ and guanosine 5'-[gamma-thio]triphosphate (GTP[S]) stimulated the formation of inositol phosphates (InsPs) in digitonin-permeabilized chromaffin cells prelabelled with [3H]inositol. The production of InsPs was potentiated by ATP. Guanosine 5'-[beta-thio]diphosphate (GDP[S]) caused a GTP-reversible shift to higher concentrations in the Ca(2+)-concentration-response curve for the release of InsPs without changing the maximal response. GTP[S] caused a shift to lower concentrations of Ca2+ and also increased the maximal response. The effects of GTP[S] and Ca2+ were synergistic. Although as much as 80% of the InsPs were derived from phosphatidylinositol 4-phosphate (PtdInsP) or 4,5-bisphosphate (PtdInsP2), the amount of InsPs produced could be several times the total amount of PtdInsP and PtdInsP2 in the cells and was largely accounted for by a decrease in PtdIns. The levels of labelled PtdInsP and PtdInsP2 increased on stimulation with Ca2+, but decreased on stimulation with GTP[S] or the combination of Ca2+ and GTP[S]. Preincubation with Ca2+ and ATP amplified the subsequent GTP[S]-induced production of InsPs. ATP and its gamma-thio and beta gamma-imido analogues stimulated the formation of InsPs in intact cells. However, only ATP potentiated the responses to Ca2+ and GTP[S] in permeable cells. Our main conclusions are: (1) a GTP-binding protein participates in the Ca(2+)-induced production of InsPs by phospholipase C, and (2) ATP markedly potentiates the stimulated formation of InsPs, an effect with arises from its role in polyphosphoinositide synthesis and does not involve purinergic receptor activation in permeabilized cells. The data also suggest that the different effects of Ca2+ and GTP[S] on polyphosphoinositide synthesis probably contribute to the synergistic action of Ca2+ and GTP[S] on the generation of InsPs.

Adenosine Triphosphate↗
PubMed1991

Calcium promotes the accumulation of polyphosphoinositides in intact and permeabilized bovine adrenal chromaffin cells.

1. Because cellular pools of phosphatidylinositol phosphate and phosphatidylinositol bisphosphate turn over rapidly during phospholipase C stimulation, the continuing production of inositol phosphates requires continuing synthesis from phosphatidylinositol of the polyphosphoinositides. In the present study in adrenal chromaffin cells, we examined the effects of nicotinic stimulation and depolarization in intact cells and micromolar Ca2+ in permeabilized cells on the levels of labeled polyphosphoinositides. We compared the effects to muscarinic stimulation in intact cells and GTP gamma S in permeabilized cells. 2. Nicotinic stimulation, elevated K+, and muscarinic stimulation cause similar production of inositol phosphates (D. A. Eberhard and R. W. Holz, J. Neurochem. 49:1634-1643, 1987). Nicotinic stimulation and elevated K+ but not muscarinic stimulation increased the levels of [3H]inositol-labeled phosphatidylinositol phosphate by 30-60% and [3H]phosphatidylinositol bisphosphate by 25-30%. The increase required Ca2+ in the medium, was maximal by 1-2 min, and was not preceded by an initial decrease in phosphatidylinositol phosphate and phosphatidylinositol bisphosphate. 3. In digitonin-permeabilized cells, Ca2+ caused as much as a twofold increase in [3H]phosphatidylinositol phosphate and [3H]phosphatidylinositol bisphosphate. Similarly, Ca2+ enhanced the production of [32P]phosphatidylinositol phosphate and [32P]phosphatidylinositol bisphosphate in the presence of [gamma-32P]ATP. In contrast, GTP gamma S in permeabilized cells decreased polyphosphoinositides in the presence or absence of Ca2+. 4. The ability of Ca2+ to increase the levels of the polyphosphoinositides decayed with time after permeabilization. The effect of Ca2+ was increased when phosphoesterase and phospholipase C activities were inhibited by neomycin. 5. These observations suggest that Ca2+ specifically enhances polyphosphoinositide synthesis at the same time that it activates phospholipase C.

Adrenal Medulla↗
PubMed1990

Evidence that the inositol phospholipids are necessary for exocytosis. Loss of inositol phospholipids and inhibition of secretion in permeabilized cells caused by a bacterial phospholipase C and removal of ATP.

We directly manipulated the levels of PtdIns, PtdInsP and PtdInsP2 in digitonin-treated adrenal chromaffin cells with a bacterial phospholipase C (PLC) from Bacillus thuringiensis and by removal of ATP. The PtdIns-PLC acted intracellularly to cause a large decrease in [3H]inositol- or [32P]phosphate-labelled PtdIns, but did not directly hydrolyse PtdInsP or PtdInsP2. [3H]PtdInsP and [3H]PtdInsP2 levels declined markedly, probably because of the action of phosphatases in the absence of synthesis. Removal of ATP also caused marked decreases in [3H]PtdInsP and [3H]PtdInsP2. The decrease in polyphosphoinositide levels by PtdIns-PLC treatment or ATP removal was reflected by the inhibition of the production of inositol phosphates upon subsequent activation of the endogenous PLC by Ca2(+)-dependent catecholamine secretion from permeabilized cells was strongly inhibited by PtdIns-PLC treatment and by ATP removal. Ca2(+)-dependent secretion was similarly correlated with the sum of PtdInsP and PtdInsP2 when the level of these lipids was changed by either manipulation. PtdIns-PLC inhibited only the ATP-dependent component of secretion and did not affect ATP-dependent secretion. Both PtdIns-PLC and ATP removal inhibited the late slow phase of secretion, but had little effect on the initial rapid phase. Although we found a tight correlation between polyphosphoinositide levels and secretion, endogenous phospholipase C activity (stimulated by Ca2+, guanine nucleotides and related agents) was not correlated with secretion. Additional experiments indicated that neither the products of the PtdIns-PLC reaction (diacylglycerol and InsP1) nor the inability to generate products by subsequent activation of the endogenous PLC is likely to account for the inhibition of secretion. Incubation of permeabilized cells with neomycin in the absence of ATP maintained the level of polyphosphoinositides and more than doubled subsequent Ca2(+)-dependent secretion. The data suggest that: (1) Ca2(+)-dependent secretion has a requirement for the presence of inositol phospholipids; (2) the enhancement of secretion by ATP results in part from increased polyphosphoinositide levels; and (3) the role for inositol phospholipids in secretion revealed in these experiments is independent of their being substrates for the generation of diacylglycerol and InsP3.

Adenosine Triphosphate↗
PubMed1989

MgATP-independent and MgATP-dependent exocytosis. Evidence that MgATP primes adrenal chromaffin cells to undergo exocytosis.

The MgATP dependency of secretion was investigated in digitonin-permeabilized adrenal chromaffin cells. Shortly after permeabilization there is a component of Ca2+-dependent secretion that occurs in the absence of MgATP in the medium. This secretion occurs from cells which are permeable to Ca2+/[ethylene-bis(oxyethylenenitrilo)]tetraacetic acid buffers, to nucleotides, and to proteins. It is prevented by treatment of cells with metabolic inhibitors to reduce cellular ATP prior to permeabilization. The rate of MgATP-independent secretion is rapid and terminates by approximately 2 min after introduction of Ca2+. MgATP-independent secretion is labile and is lost unless Ca2+ is introduced within 8 min of permeabilization. MgATP-dependent secretion occurs at a slower rate than MgATP-independent secretion and continues at a constant rate for 12 min. Preincubation of permeabilized cells with MgATP enhances Ca2+-dependent secretion during a subsequent incubation in the absence of MgATP. Similar MgATP sensitivities are observed when MgATP is present only prior to or only during stimulation with Ca2+ with half-maximal stimulation occurring at 0.4-0.5 and 0.6 mM MgATP, respectively. The data indicate that intact cells are primed by intracellular ATP so that immediately upon permeabilization, there is a component of secretion which is independent of medium MgATP. MgATP partially maintains the primed state after permeabilization by acting before Ca2+ in the secretory pathway.

Adenosine Triphosphate↗
PubMed1987

Cholinergic stimulation of inositol phosphate formation in bovine adrenal chromaffin cells: distinct nicotinic and muscarinic mechanisms.

The ability of cholinergic agonists to activate phospholipase C in bovine adrenal chromaffin cells was examined by assaying the production of inositol phosphates in cells prelabeled with [3H]inositol. We found that both nicotinic and muscarinic agonists increased the accumulation of [3H]inositol phosphates (mainly inositol monophosphate) and that the effects mediated by the two types of receptors were independent of each other. The production of inositol phosphates by nicotinic stimulation required extracellular Ca2+ and was maximal at 0.2 mM Ca2+. Increasing extracellular Ca2+ from 0.22 to 2.2 mM increased the sensitivity of inositol phosphates formation to stimulation by submaximal concentrations of 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP) but did not enhance the response to muscarine. Elevated K+ also stimulated Ca2+-dependent [3H]inositol phosphate production, presumably by a non-receptor-mediated mechanism. The Ca2+ channel antagonists D600 and nifedipine inhibited the effects of DMPP and elevated K+ to a greater extent than that of muscarine. Ca2+ (0.3-10 microM) directly stimulated the release of inositol phosphates from digitonin-permeabilized cells that had been prelabeled with [3H]inositol. Thus, cholinergic stimulation of bovine adrenal chromaffin cells results in the activation of phospholipase C by distinct muscarinic and nicotinic mechanisms. Nicotinic receptor stimulation and elevated K+ probably increased the accumulation of inositol phosphates through Ca2+ influx and a rise in cytosolic Ca2+. Because Ba2+ caused catecholamine secretion but did not enhance the formation of inositol phosphates, phospholipase C activation is not required for exocytosis. However, diglyceride and myo-inositol 1,4,5-trisphosphate produced during cholinergic stimulation of chromaffin cells may modulate secretion and other cellular processes by activating protein kinase C and/or releasing Ca2+ from intracellular stores.

Adrenal Medulla↗
PubMedDate not supplied

Two-year-old boy with Proteus syndrome and fatal pulmonary thromboembolism.

A 2-year-old boy with a relatively mild form of Proteus syndrome (PS) died suddenly during a previously uncomplicated postsurgical convalescence. Autopsy demonstrated massive acute pulmonary embolism, which has not been previously reported in PS. In addition, clinically occult mesodermal hamartomata, predominantly hemolymphangiomata, were found to be widespread in the pelvoabdominal viscera, including spleen, appendix, kidneys, adrenal gland, liver, and retroperitoneal soft tissues. Such lesions may well be common in PS patients but may not be detected by conventional radiographic imaging techniques unless they are fairly large.

Child, Preschool↗
PubMedDate not supplied

Pleomorphic xanthoastrocytoma, a distinctive astroglial tumor: neuroradiologic and pathologic features.

PURPOSE: To analyze and discuss CT and MR features of pleomorphic xanthoastrocytoma (PXA) and present salient histopathologic features of this distinctive astroglial tumor. METHOD: CT, MR, and histopathologic studies on seven patients with the histologic diagnosis of PXA were reviewed retrospectively. RESULTS: All patients were in their first 3 decades of life when first diagnosed and demonstrated peripherally situated supratentorial tumors of varying size involving the superficial cortex and leptomeninges. Five of six cases examined with CT showed areas of mixed attenuation with four demonstrating well-demarcated enhancement. MR demonstrated low or mixed signal intensity on T1-weighted and high or mixed signal intensity on T2-weighted sequences. All five who received gadopentetate dimeglumine showed well-defined enhancement. Three showed cyst formation. Typical histologic features included marked cellular pleomorphism with giant cells, bizarre nuclei, variable cytoplasmic lipidization and positive immunoreactivity for glial fibrillary acidic protein. Necrosis and endothelial-pericytic cell proliferation were absent. CONCLUSION: PXA has a highly suggestive neuroradiologic and distinctive histopathologic appearance.

Adolescent↗